Calcium carbonate, usually in the form of a powder derived from naturally occuring mineral deposits, e.g., limestone, dolomite, or marble, have been in the past employed in various functions in combination with certain binders and other materials to form articles of manufacture.
For example, U.S. Pat. No. 3,366,720 suggests producing building blocks by dry mixing 1 to 15 parts by volume of a rock selected from a group consisting of granite, quartz, feldspar, limestone, slate, marble, porphyry, sandstone, syenite, basalt, diabase, trachyte, dolomite, and gneiss with one part hydraulic cement and a small amount of calcium chloride, compressing these materials under high pressure and curing the thus formed block with steam under pressure. These base materials are characterized as particles of rock "of hard type".
In U.S. Pat. No. 3,231,657, an insulating material of the calcium silicate type is formed by molding in mold halves a slurry of lime, silica and water. Thus molded, the articles are cured under pressurized, saturated steam conditions for a time period from 1 to up to 15 hours. To these basic ingredients (quick lime, silica, and water) may be added to other ingredients in minor amounts. Example 1 shows asbestos, clay and "inerts, e.g., limestone, etc." are added. The function of these fillers and inert materials are not directly stated.
In another process set forth in U.S. Pat. No. 2,602,754 magnesium sulphate and pressure hydrated dolomite is added to the slurry to impart the feel and softness simulating that of well known 85% magnesia insulation.
Calcium carbonate in the form of limestone and marble has also been used in non-autoclave cured compositions. One example of this is shown in U.S. Pat. No. 662,643 wherein plaster of paris, hydraulic cement and ground or pulverized shale and limestone or marble are combined and used for a wall plaster on lathing. A quantity of "any of the ordinary fibers" may be incorporated, such as wood fiber.
Another example is shown in U.S. Pat. No. 1,861,317 which discloses a cement sizing between stucco, masonry, and plaster surfaces and an outer coating of oil paint or similar surface preparation. This sizing consists of a hydraulic cement such as Portland Cement, a filler of an amorphous white silica, pulverized quartz or silex, chalk, pulverized limestone, or marble or other silicious or calcareous material(s). Materials are combined with a suitable quantity of alum which is intended to react with the calcium carbonate containing materials to form calcium sulphate and aluminum hydroxide. Other materials such as casein compound, borax and hydrated lime are further included.